My slow DSL prevented me from sticking with the entire video.
But presume that it was videoed on the Columbia River bar. I had a job as Ordinary Seaman then Able Bodied Seaman sailing up/down the West Coast on Chevron oil tankers after college. Portland Oregon was frequent destination. One passage over the bar from the Pacific Ocean into the river occurred with heavy rolling breakers. Several times, the entire deck of the loaded tanker (= free-board was only say 8-10 ft) was totally submerged. The ship was about 520 ft long. The bar pilots closed the bar right after our passage. Not only are large waves an issue, but for vessels with say 30ft draft (which we probably were that day), the keel can hit bottom with the longitudinal up/down motion and maybe being in a deep trough between two waves.